1. Field of the Invention
The present invention relates to an X-ray analyzing apparatus and a method therefor for measuring an arbitrary point of measurement of a disc shaped sample such as, for example, a wafer.
2. Description of Related Art
Hitherto, the analysis of, for example, a wafer has been carried out by irradiating a sample surface with primary X-rays, detecting secondary X-rays emanating from the sample surface and then measuring the intensity of the secondary X-rays emitted by the sample surface. In the practice of this conventional X-ray analysis, it has been well recognized that a sample of a kind having a crystalline structure, such as, for example, a wafer, when irradiated with the primary X-rays, may emit the secondary X-rays containing not only fluorescent X-rays, but also diffracted X-rays. During the X-ray fluorescence analysis, these diffracted X-rays often constitute an obstruction to the measurement and the rotative direction of the sample in which the diffracted X-rays are generated changes depending on the cut plane of the sample which may be (110) or (111) plane in the crystalline structure.
Accordingly, the fluorescence analyzing method has been known in which, prior to the X-ray fluorescence analysis of the sample, while the sample is rotated an angle equal to or greater than 180° about a predetermined point of the sample, the primary X-rays are radiated towards the sample, secondary X-rays emanating from the sample and containing fluorescent X-rays and diffracted X-rays are detected, the sample is then rotated in such a direction that the intensity of the detected secondary X-rays may exhibit the minimum value, and in this condition the sample is thereafter transferred in XY directions, which are perpendicular to each other, in a plane parallel to the measuring surface to perform the analysis over the entire measuring surface of the sample. In this respect, see, for example, the patent document 1 listed below.
Also, as shown in FIG. 11 of the accompanying drawings, when with respect to a desired point of measurement (measuring site) positioned in the vicinity of an edge of a plate-like sample measurement is carried out by positioning the point of measurement so that the primary X-rays 2 are radiated from outside of a region above the sample S and the primary X-rays 2 so radiated may undergo a total reflection towards such region, a portion of the primary X-rays 2 are radiated towards a vertical end face of the sample S, accompanied by emission of strong scattered X-rays 9 in all directions. A portion of the scattered X-rays so emitted forms a large background to the fluorescent X-rays to be measured.
In view of the foregoing, a total reflection X-ray fluorescence spectrometer has been made available, in which with respect to an arbitrary point of measurement located in the vicinity of the edge of the sample, measurement is carried out by positioning the point of measurement so that the primary X-rays 2 are radiated from the region above the sample S and the primary X-rays 2 so radiated may undergo a total reflection towards outside of such region, to thereby suppress the scattered X-rays emitted from the end face of the sample. In this respect, see, for example, the patent document 2 listed below.